Re-understanding speech understanding: Closing the cohort loop

Human listeners understand spoken language literally as they hear it, reflecting a perceptually seamless process of real-time comprehension of what the speaker is saying. This remarkable experience of immediacy is rooted in the exceptional earliness with which information carried by successive words is integrated into the interpretation of the current utterance. But despite 50 years of research, there has been no accepted mechanistic neurobiological account of the brain systems that support this process. Only recently have scientific tools emerged that allow us to probe the real-time activity of these brain systems, telling us where and when such activity can be detected and what their neurocomputational content might be. The resulting research enables us, first, to reject the historically dominant account of early speech interpretation as a linguistically stratified computational hierarchy, centered around the notion of a phoneme, and based on sequential transitions between successive representational states.